Hi Am 07.10.22 um 09:15 schrieb Ville Syrjälä:
For the absolute size of fbdev memory, I think we should introduce a module parameter in drm_fb_helper, which an option to set a default value in the kernel config. It would benefit all drivers that use fbdev emulation and work how overalloc works. If no size is given, the current approach would be used. I don't think resizing would work immediately. There isn't anything in the check_var and set_par functions that implements the necessary atomic check and commit.set_par() is the thing tht does the commit.
I know. There actually even is a commit statement in set_par, which can restore the initial mode. My point is that it has no means of changing the display mode. A full modeset would require us to convert the fb screeninfo into an atomic state and commit that instead. For the fbconv helper, I once made code to convert between the two. Leaving this here for reference. [1][2]
Similarly, in check_var we sort out and reject all mode changes. We'd have to change that as well.
I guess we can continue to ignore non-atomic modesetting. Best regards Thomas[1] https://gitlab.freedesktop.org/tzimmermann/linux/-/commit/385161cd2d048b5cf80544bff8ced3da7a82dfa9 [2] https://gitlab.freedesktop.org/tzimmermann/linux/-/commit/a541c405a638f47ee80389b222fbde6e311e8220
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Ivo Totev
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